U.S. patent number 9,597,046 [Application Number 14/359,967] was granted by the patent office on 2017-03-21 for method and device for imaging soft body tissue using x-ray projection and optical tomography.
This patent grant is currently assigned to KONINKLIJKE PHILIPS N.V.. The grantee listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Andre Goossen, Harald Sepp Heese, Thomas Koehler.
United States Patent |
9,597,046 |
Goossen , et al. |
March 21, 2017 |
Method and device for imaging soft body tissue using X-ray
projection and optical tomography
Abstract
Soft body tissue, such as a female breast, is imaged using X-ray
projection techniques and optical tomography techniques. First
image data for a first image of a breast (17) are acquired by X-ray
projection using an X-ray source (3) and an X-ray detector (5).
Second image data for a second image are acquired using optical
tomography equipment comprising a light source (9) and a light
detector (11). From the first image data, estimated bulk optical
properties of the breast (17) are be derived. Based on such
estimated bulk optical properties, an optical tomography image is
reconstructed from the second image data with high image quality.
Performing mammography acquisition at different compression states
of the breast (17) improves patient comfort. Mammograms are
acquired at two different compression states wherein a first
compression state is adapted to provide high image resolution. At a
second compression state, another mammogram may be acquired
together with an optical tomography image. The two mammograms are
used for image registration thereby possibly providing information
for a deformation transform. Additional information on tissue
composition within the breast is received by acquiring the first
and second mammogram at different X-ray settings.
Inventors: |
Goossen; Andre (Radbruch,
DE), Heese; Harald Sepp (Hamburg, DE),
Koehler; Thomas (Norderstedt, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
N/A |
NL |
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Assignee: |
KONINKLIJKE PHILIPS N.V.
(Eindhoven, NL)
|
Family
ID: |
47471874 |
Appl.
No.: |
14/359,967 |
Filed: |
November 13, 2012 |
PCT
Filed: |
November 13, 2012 |
PCT No.: |
PCT/IB2012/056382 |
371(c)(1),(2),(4) Date: |
May 22, 2014 |
PCT
Pub. No.: |
WO2013/076616 |
PCT
Pub. Date: |
May 30, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140288420 A1 |
Sep 25, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61563091 |
Nov 23, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
5/0091 (20130101); A61B 5/7425 (20130101); A61B
5/0035 (20130101); A61B 6/502 (20130101); G16H
50/30 (20180101); A61B 6/463 (20130101); A61B
6/5247 (20130101); A61B 6/4417 (20130101); A61B
6/5217 (20130101); A61B 6/482 (20130101); A61B
5/0073 (20130101); A61B 6/54 (20130101); A61B
6/0414 (20130101) |
Current International
Class: |
A61B
5/05 (20060101); A61B 5/00 (20060101); A61B
6/00 (20060101); A61B 6/04 (20060101) |
Field of
Search: |
;600/407-430,473-480 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Azar et al: "Standardized Platform for Coregistration of
Nonconcurrent Diffuse Opetical Magnetic Resonance Breast Images
Obtained in Different Geometries": Journal of Biomedical Optics,
vol. 12, No. 5, Jan. 2007, pp. 051902-051902-14. cited by applicant
.
Chiang et al: "Dual-Direction Measuring System of Near Infrared
Optical Tomography Combined With X-Ray Mammography"; MVA2011
Conference on Machine Vision Applications, Jun. 2011, Nara, Japan,
pp. 540-543. cited by applicant .
Fang et al: "Combined Optical Imaging and Mammography of the
Healthy Breast: Optical Contrast Derived From Breast Structure and
Compression"; IEEE Transactions on Imaging, vol. 28, No. 1, Jan.
2009, pp. 30-42. cited by applicant .
Li et al : "Tomographic Optical Breast Imaging Guided by
Three-Dimensional Mammography"; Applied Optics, Sep. 2003, vol. 42.
No. 25, pp. 5181-5190. cited by applicant.
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Primary Examiner: Cattungal; Sanjay
Parent Case Text
CROSS-REFERENCE TO PRIOR APPLICATIONS
This application is the U.S. National Phase application under 35
U.S.C. .sctn.371 of International Application No.
PCT/IB2012/056382, filed on Nov. 13, 2012, which claims the benefit
of U.S. Provisional Patent Application No. 61/563091, filed on Nov.
23, 2011. These applications are hereby incorporated by reference
herein.
Claims
The invention claimed is:
1. A method of imaging a soft body tissue, the method comprising:
acquiring first image data for a first image of a region of
interest of the soft body tissue using X-ray projection; acquiring
second image data for a second image of the region of interest of
the soft body tissue using optical tomography; deriving estimated
bulk optical properties of the soft body tissue in the region of
interest from the acquired first image data; reconstructing the
second image from the second image data using the estimated bulk
optical, properties; and acquiring third image data for a third
image of the region of interest of the soft body tissue using X-ray
projection, wherein the first image data is acquired with the soft
body tissue being in a first compression state and the second and
third image data is acquired with the soft body tissue being in a
different second compression state at lower compression than in the
first compression state.
2. The method of claim 1, further comprising: elastically
registering the first image data and the third image data thereby
deriving a transform relating the first and second compression
states of the soft body tissue.
3. The method of claim 2, further comprising: transforming the
estimated bulk optical properties using the transform; and
reconstructing the second image from the second image data
additionally using such transformed estimated bulk optical
properties.
4. The method of claim 1, wherein the first image data is acquired
with a first setting for X-ray energy, X-ray spectrum and/or X-ray
dose, and wherein the third image data is acquired with a different
second setting for X-ray energy, X-ray spectrum and/or X-ray
dose.
5. The method of claim 4, further comprising: deriving estimated
information on tissue composition of the soft body tissue in the
region of interest taking into account the acquired first image
data and the acquired third image data; deriving the estimated bulk
optical properties of the soft body tissue in the region of
interest from the estimated information on tissue composition; and
reconstructing the second image from the second image data using
such estimated bulk optical properties.
6. The method of claim 1, wherein the second image data is acquired
using diffuse optical tomography.
7. The method of claim 1, further comprising: displaying a
registered superposition of a 2-dimensional image derived from the
reconstructed second image and the first image.
8. An imaging device, comprising: a soft body tissue compressor for
compressing a soft body tissue to at least two different
compression states; an X-ray source and an X-ray detector arranged
at opposite sides of the soft body tissue compressor; an optical
tomography light source and an optical tomography light detector
arranged at opposite sides of the soft body tissue compressor; and
at least one computer configured to perform the method according to
claim 1.
9. The imaging device of claim 8, wherein the device is adapted to
automatically control at least one of the soft body tissue
compressor, the X-ray source, the X-ray detector, the optical
tomography light source and the optical tomography light
detector.
10. A non-transitory computer readable medium having stored thereon
computer readable instructions for instructing a computer to
perform the method according to claim 1.
11. A method of imaging breast tissue, the method comprising:
compressing a breast to a first compression state; with the breast
in the first compression state, generating first image data of the
breast; compressing the breast to a second compression state, the
second compression state being less compressed than the first
compression state; with the breast in the second compression state,
generating second image data using optical tomography and
generating third image data; with at least one processor,
determining a transform relating the first compression state and
the second compression state based on the first and third image
data; with the at least one processor, derive estimated bulk
optical properties of the breast from the first image data and
transform the estimation of the bulk optical properties to the
second compression state with the determined transform; with the at
least one processor, reconstructing an optical tomographic image of
the breast from the second image data and the transformed
estimation of the bulk optical properties; and displaying the
optical diagnostic image on a display device.
12. The method according to claim 11, wherein the first and third
image data include X-ray projection image data, the first and third
image data being generated with different X-ray settings, and
further including: with the at least one processor, performing a
dual-energy volumetric breast density assessment based on the first
and third image data.
13. The method according to claim 12, wherein the soft tissue
includes a breast.
14. The method according to claim 11, further including: with the
at least one processor, combining the optical tomographic image
with an image generated from one of the first and third image data;
and displaying the combined image on the display device.
15. An imaging apparatus for imaging soft body tissue, the
apparatus comprising: a compression device including at least one
compression panel configured for compressing a soft tissue to a
first compression state and to a second compression state, the
second compression state being less compressed than the first
compression state; an X-ray imaging system configured to: with the
soft tissue in the first compression state, generating first image
data of the soft tissue, and with the soft tissue in the second
compression state, generating third image data, an optical imaging
system configured to generate second image data; at least one
processor configured to: determine a transform relating the first
compression state and the second compression state based on the
first and third image data, derive estimated bulk optical
properties of the soft tissue from the first image data,
reconstruct an optical tomographic image of the soft tissue based
on the second image data, the transform, and the estimated bulk
optical properties; and a display device configured to display the
optical tomographic image.
16. The apparatus according to claim 15, wherein the at least one
processor is further configured to: perform a dual-energy
volumetric breast density assessment based on the first and third
image data.
17. The apparatus according to claim 15, wherein the at least one
processor is further configured to: combine the optical tomographic
image with an image generated from one of the first and third image
data and display the combined image on the display device.
Description
FIELD OF THE INVENTION
The present invention relates to a method and a device for imaging
soft body tissue such as a female breast. Furthermore, the
invention relates to a computer program product for performing such
method and a computer-readable medium having stored thereon such
computer program product.
BACKGROUND OF THE INVENTION
In order to be able to examine soft body tissue such as a female
breast and possibly detect tumourous tissue therein, various
imaging methods have been developed.
For example, mammography imaging uses X-rays which are projected
through the breast and are detected after transmission such that,
from the detected X-ray intensity distribution, information may be
derived with respect to geometry and X-ray absorption of structures
within the breast. The images acquired by a mammography X-ray
projection are typically two-dimensional (2D).
As an alternative imaging technique, optical tomography has been
developed. Optical tomography is a type of computer tomography that
generates a digital volumetric model of an object by reconstructing
three-dimensional images made from light transmitted and scattered
through the object. Therein, optical tomography uses the fact that
the object is typically at least partially light-transmitting or
translucent. Accordingly, these techniques are best suitable for
soft tissues such as present in a female breast. For example, in
diffuse optical tomography (DOT) light in the near infrared
spectrum is transmitted through a soft tissue object and detected
after transmission. From data of detected light intensity,
information about structural properties and material properties
within the soft tissue volume may be derived due to differing
diffusive characteristics of various tissue types. For example,
information about local concentrations of oxygenated haemoglobin
and deoxygenated haemoglobin may be obtained by DOT and such
information may allow deriving additional information about
functional properties of tissue comprised in a region of interest.
Three-dimensional (3D) images may be reconstructed from such
acquired optical tomography image data. The spatial resolution of
e. g. diffusive optical tomography techniques is typically rather
coarse, e.g. in a range of several millimeters.
Qianqian Fang; Carp, S. A.; Selb, J.; Boverman, G.; Quan Zhang;
Kopans, D. B.; Moore, R. H.; Miller, E. L.; Brooks, D. H.; Boas, D.
A.; , "Combined Optical Imaging and Mammography of the Healthy
Breast: Optical Contrast Derived From Breast Structure and
Compression," Medical Imaging, IEEE Transactions on , vol. 28, no.
1, pp. 30-42, January 2009 doi: 10.1109/TMI.2008.925082 discloses
combined X-ray mammography/diffusive optical breast imaging.
However, the proposed approach still suffers from shortcomings
concerning e.g. image quality and/or patient comfort.
SUMMARY OF THE INVENTION
There may be a need e.g. for a method of imaging soft body tissue
such as a female breast and for a device implementing such method
allowing improved visualization of structures and tissue
characteristics occurring within a region of interest of the soft
body tissue. Particularly, there may be e.g. a need for an imaging
method and device providing information on soft body tissue
characteristics at high spatial resolution. Furthermore, there may
be a need for a computer program product adapted for implementing
such method on a computer and for a computer-readable medium having
stored thereon such computer program product.
At some of the needs resulting from shortcomings of prior art
approaches may be met by the subject-matter of the independent
claims. Further embodiments of the invention are defined in the
dependent claims.
According to a first aspect of the present invention, a method of
imaging a soft body tissue is proposed to comprise the following
steps: (a) acquiring first image data for a first image of a region
of interest of the soft body tissue using X-ray projection; (b)
acquiring second image data for a second image of the region of
interest of the soft body tissue using optical tomography; (c)
deriving estimated bulk optical properties of the soft body tissue
in the region of interest from the acquired first image data; and
(d) reconstructing the second image from the second image data
using the derived estimated bulk optical properties.
The method steps can be performed in a different order than
indicated. For example, the order of steps (a) and (b) may be
inversed.
A general idea underlying the first aspect of the invention may be
seen in realizing synergy effects by acquiring image data using two
different types of imaging, i. e. X-ray projection imaging and
optical tomography imaging, wherein not only the advantages of each
of the imaging techniques are combined but further advantageous
effects may be achieved.
For example, benefit may be taken from the fact that first image
data acquired using X-ray projection may provide for
two-dimensional images representing X-ray absorption
characteristics of the radiographed soft body tissue at high
spatial resolution. From such first image data an estimation of
optical properties in the bulk of the soft body tissue may be
derived. Such information may subsequently be used to improve the
reconstruction of a second image from second image data acquired
using optical tomography techniques. Typically, such second image
reconstruction may be complex and may suffer from inaccuracies as
in such reconstruction specific assumptions generally have to be
taken before initiating the reconstruction. The determination of
such assumptions is generally complicated and may result in
inaccuracies in the reconstructed image. Inter alia, such
assumptions may relate to bulk optical properties present in the
soft body tissue to be imaged using optical tomography as such bulk
optical properties may influence the transmission and diffusion of
light used for the optical tomography imaging.
It is proposed herein to provide a high quality estimate for such
bulk optical properties by deriving estimated bulk optical
properties of the soft body tissue from previously acquired X-ray
projection image data allowing deriving bulk optical properties at
high spatial resolution. Using such estimated bulk optical
properties, the reconstruction of the optical tomography image may
be improved and may, inter alia, show increased spatial
resolution.
Embodiments of the proposed method may be specifically used for
imaging a female breast. The first image data may then be acquired
using mammography X-ray projection and the first image may also be
referred to as a mammogram. In such imaging of a female breast, the
second image data may be advantageously acquired using diffused
optical tomography (DOT). DOT may provide for a three-dimensional
image including functional information about the tissue comprised
in a region of interest.
The proposed imaging method may further comprise an additional
process step of acquiring third image data for a third image of the
region of interest of the soft body tissue using X-ray projection.
Therein, the first image data is acquired with the soft body tissue
being in a first compression state and the second and third image
data is acquired with the soft body tissue being in a different
second compression state at lower compression than in the first
compression state.
The acquisition of third image data may further improve the
reconstruction of the second image acquired by optical tomography.
Particularly, it may be beneficial to acquire first image data of
e. g. a female breast at high compression of the breast and,
additionally, acquire third image data at lower compression of the
breast, both image data being acquired using X-ray projection.
While, at high compression of the breasts, a mammogram of high
quality and high information content may be acquired, the high
compression may be uncomfortable for the patient. As optical
tomography requires relatively long illumination periods, the
second image data using optical tomography may be acquired at lower
compression of the breast thereby considerably improving comfort of
the patient. In order to better correlate the first image data and
the second image data, these first and second image data being
acquired using different imaging techniques and at different
compression states, third image data are further acquired, these
third image data being acquired with the same technique as the
first image data and at the same compression state as the second
image data.
For example, the first image data and the third image data may be
elastically registered to one another. Thereby, a so-called
"deformation prior" relating to the first and second compression
state of the breast may be derived. This deformation prior may
comprise information about how the examined soft body tissue is
deformed between the first compression state and the second
compression state. Such information may be advantageously used in
subsequently reconstructing the second image from the second image
data.
For example, bulk estimated optical properties of the soft body
tissue derived from the first image data, being acquired at high
compression, may be transformed using the information contained in
the transformation prior. The second image may then be
reconstructed from the second image data, acquired at low
compression, while additionally using such transformed bulk optical
properties.
In other words, bulk optical properties may first be estimated by
deriving information from the first image data which have been
acquired with X-ray projection at high compression of the soft body
tissue and therefore comprise high resolution detailed structural
information about local absorption in the soft body tissue. Then,
in order to improve the patient's comfort, the compression of the
soft body tissue may be reduced and second and third image data may
be acquired using optical tomography and using X-ray projection,
respectively. The high quality information comprised in the first
image data may then be used for estimating bulk optical properties.
In principle, such bulk optical properties could also be derived
from the third image data, acquired at lower compression, but with
lower information quality as X-ray projection at such lower
compression typically results in images having lower spatial
resolution and/or less information about local X-ray absorption.
Therefore, the detailed information on bulk optical properties
derived from the first image data is to be used and is then
transformed to the geometry of the soft body tissue taken in the
second lower compression state. Therein, the information obtained
by registering the first image data and the third image data, both
being acquired with X-ray projection but in different compression
states, may be used as deformation prior in transforming the
estimated bulk optical properties which have previously been
derived from the high quality first image data. Thus, the
information about the bulk optical properties is maintained at high
quality but is transformed into the geometry which is taken by the
soft body tissue in the second compression state at which also the
second image data is acquired using optical tomography.
Accordingly, the second image may finally be reconstructed at high
quality from the second image data using such transformed bulk
optical properties.
In the proposed method, the first image data may be acquired with a
first setting for X-ray energy, X-ray spectrum and/or X-ray dose
and the third image data may be acquired with a different second
setting for X-ray energy, X-ray spectrum and/or X-ray dose.
In such embodiment, benefit may be taken from the fact that soft
body tissue may have different X-ray absorption characteristics at
different settings for the radiation used for the X-ray projection.
In other words, a specific type of soft body tissue may have
different X-ray absorption characteristics at different X-ray
energy, X-ray spectrum and/or x-ray dose than another type of soft
body tissue. Accordingly, by using different settings for the X-ray
radiation used in acquiring the first image data and third image
data, respectively, additional information on the local
distribution of tissue types in the soft body tissue may be
acquired.
For example, estimated information on tissue composition of the
soft body tissue in the region of interest may be derived taking
into account the acquired first image data and the acquired third
image data. Subsequently, estimated bulk optical properties of the
soft body tissue in the region of interest may be derived from the
estimated information on tissue composition. Finally, the second
image may be reconstructed from the second image data using such
estimated bulk optical properties.
Accordingly, in such embodiment, estimated bulk optical properties
may be derived not only based on a single data acquisition with
X-ray projection, i.e. the first image data, but on two data
acquisitions using X-ray projection at different X-ray settings.
From these two image data, additional information may be derived,
such additional information relating to tissue composition in the
region of interest of the soft body tissue. As the optical
properties within the region of interest may, inter alia, depend on
the local tissue composition, this additional information may then
be used for a more precise estimate of the bulk optical properties
in the region of interest. Such improved estimate may result in
enabling improved reconstruction of the second image, i.e. the
optical tomography image.
The reconstructed second image may be displayed together with the
first image. Both images may relate to different information
content. For example, the second image may comprise information on
physiological functions within the soft body tissue whereas the
first image may comprise detailed geometrical information on
structures within the soft body tissue.
The first and second images may be displayed as a registered
superposition of a two-dimensional second image derived from the
reconstructed three-dimensional second image and of the
two-dimensional first image.
Therein, the 2D second image may e.g. be derived from the
reconstructed 3D second image for example by calculating a 2D
projection through the 3D second image with respect to an imaging
plane corresponding to the imaging plane at which the first image
is acquired by X-ray projection. Alternatively, the 2D second image
may e.g. be derived from the reconstructed 3D second image for
example by calculating a 2D slice of the 3D second image in a plane
parallel to the imaging plane at which the first image is
acquired.
While the first and second 2D images may be acquired at different
compression states of the soft body tissue and may therefore relate
to different geometrical states of the region of interest in the
soft body tissue, these two 2D images may be superpositioned after
registering the images. The registration may comprise a
transformation of the first 2D image, acquired in a first
geometrical state of the soft body tissue at high compression, to a
second geometrical state of the soft body tissue at low compression
at which the second image data have been acquired, or vice versa.
After such transformation, both 2D images may be superpositioned
and displayed to the user, thereby enabling simplified image
analysis by the user.
According to a further aspect of the present invention, an imaging
device is proposed. This imaging device is adapted for performing
embodiments of the above-identified imaging method.
For example, the imaging device may comprise a soft body tissue
compressor for compressing the soft body tissue at different
compression states. Furthermore, an X-ray source and an X-ray
detector arranged on opposite sides of the soft body tissue
compressor as well as an optical tomography light source and an
optical tomography light detector arranged on opposite sides of the
soft body tissue compressor, are provided. Furthermore, a computer
adapted to performing the above-defined method in one of its
embodiments is comprised in the imaging device.
The imaging device may be adapted to automatically control at least
one of the soft body tissue compressors, the X-ray source, the
X-ray detector, the optical tomography light source and the optical
tomography light detector.
Accordingly, the imaging device may be adapted to automatically
acquire first, second and, optionally, third image data using a
respective means for X-ray projection and optical tomography,
respectively, and, possibly, bringing the soft body tissue to
specific different compression states using the soft body tissue
compressor.
According to a third aspect of the present invention, a computer
program product is proposed to comprise computer-readable
instructions for instructing a computer to perform a method
according to an embodiment of the above-identified method. Such
computer program product may be stored on a computer-readable
medium. The computer program product may use computer-readable
instructions in any suitable programming language to acquire image
data from respective imaging means, process such data and finally
output such data for e.g. visualization. The computer-readable
medium may be any type of medium adapted for storing
computer-readable instructions such as e.g. CDs, DVDs, flash
memory, etc.
It has to be noted that aspects and embodiments of the present
invention and possible features and advantages thereof are
described herein with reference to different subject-matters. In
particular, some embodiments are described with reference to method
type claims whereas other embodiments are described with reference
to device type claims. However, a person skilled in the art will
understand from the above and the following description that,
unless other notified, in addition to any combination of features
belonging to one type of subject-matter also any combination
between features relating to different subject-matters, in
particular between features of the device type claims and features
of the method type claims, is considered to be disclosed with this
application.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention are described in the following
with reference to the enclosed figures. Neither the description nor
the figures shall be interpreted as limiting the invention.
FIG. 1 shows an imaging device according to an embodiment of the
present invention.
FIGS. 2(a), (b) show mammograms acquired at normal and reduced
compression.
The figures are only schematically and not to scale.
DETAILED DESCRIPTION OF EMBODIMENTS
FIG. 1 shows an imaging device 1 which may be used for performing
an imaging method according to embodiments of the present invention
as described in further detail below. The imaging device 1 is
adapted for imaging a female breast 17 at different compression
states and with different imaging modalities.
The imaging device 1 comprises a soft body tissue compressor 15
having a compression paddle 13 which may be moved in a vertical
direction 23 as indicated in FIG. 1. Using the movable compression
paddle 13, a female breast 17 interposed between the compression
paddle 13 and a housing 21 may be compressed to different
compression states as schematically indicated in the figure by
dotted and solid lines, respectively.
An X-ray source 3 and an X-ray detector 5 are arranged at opposite
sides of the compressor 15. The X-ray source 3 may emit X-rays
towards a region of interest within the breast 17 such that these
X-rays are transmitted through the region of interest and are
subsequently detected by the X-ray detector 5. Accordingly,
mammography X-ray projections may be acquired.
The X-ray source 3 may be operated at different operating
conditions such as e.g. different acceleration voltages, electron
flow densities, etc., such that an energy, a spectrum and/or a dose
of X-rays emitted by the X-ray source 3 may be varied. Furthermore,
filters 7 may be introduced into an X-ray beam and may be
dynamically exchangeable. By establishing such different settings
during X-ray image data acquisition, characteristics of the X-rays
emitted from the X-ray source 3 may be specifically adapted such
that different types of body tissue show differing X-ray absorption
characteristics depending on the X-ray absorptions such that,
finally, information on the tissue composition within the region of
interest may be acquired with high precision.
Additionally to the components 3, 5, 7 of the radiography
equipment, components of optical tomography equipment may be
arranged adjacent to the breast 17. An optical tomography light
source 9 may be arranged on top of the transparent compression
paddle 13 and an optical tomography light detector 11 may be
arranged underneath the breast 17, for example within the housing
21 which may also be transparent to light emitted by the optical
tomography light source 9.
The optical tomography light source 9 comprises a multiplicity of
individual light emitters at different locations such that light,
for example in the near infrared (NIR) spectral range, may be
emitted towards the breast 17 and transmitted through the breast 17
at different angles towards the optical tomography light detector
11. The optical tomography light detector 11 comprises a
multiplicity of individual light detectors distributed in a matrix
such that light transmitted through the breast 17 and possibly
diffused therein may be two-dimensionally detected. By acquiring a
multiplicity of two-dimensional images using the optical tomography
light detector 11 upon light transmission through the breast at
different angles, a three-dimensional optical tomography image may
be reconstructed. In a beneficial setup, various lights sources may
be combined to obtain varying patterns of light emission which may
be detected by all sensors. This may yield quasi-angular
information which may be subsequently used for image
reconstruction. Accordingly, there may be no need for mechanical
movement of components of the DOT equipment during the DOT
acquisition.
All components of the imaging device 1, i.e. the X-ray source 3,
the X-ray detector 5, the filters 7, the optical tomography light
source 9, the optical tomography light detector 11 and a moving
mechanism (not shown) for the movable compression paddle 13 of the
compressor 15 are connected to a control 19. This control 19 may
control and operate the components automatically and acquire,
process and output data from the components in order to perform an
imaging method according to an embodiment of the present invention
as described in the following.
First, the female breast is arranged on top of the housing 21 and
underneath the compression paddle 13. By lowering the compression
paddle 13 along the direction 23, the breast 17 is compressed to a
first compression state as indicated by the dotted line in FIG.
1.
In such first compression state, first image data of the breast 17
are acquired by projecting X-rays from the X-ray source 3 through
the breast 17 towards the X-ray detector 5 and detecting the
transmitted X-rays by the detector 5. For such mammography X-ray
projection, standard settings for X-ray energy, X-ray spectrum,
X-ray dose and the selection of the filter material 7 may be
used.
Subsequently, the compression to the breast 17 is reduced by moving
the compression paddle 17 upwards. Thereby, a second compression
state of the breast 17 as indicated in FIG. 1 by the solid line may
be obtained.
In such second compression state, another mammogram is acquired. In
other words, third image data of the region of interest of the
breast 17 are acquired by X-ray projection. In such X-ray
projection at the second compression state of reduced compression,
different settings for the X-ray source 3 and/or the filters 7 may
be used. For example, an acceleration voltage of the X-ray source 3
may be increased and an electron flow density may be reduced and
the filter introduced into the X-ray beam may be exchanged such
that the third image data are acquired with high X-ray photon
energy at low-dose.
Then, the optical tomography light source 9 and the optical
tomography light detector 11 may be arranged adjacent to the breast
17 while keeping the breast 17 in the second compression state.
Using this optical tomography equipment 9, 11, second image data of
the region of interest of the breast 17 are acquired.
After such image data acquisition, the breast 17 may be released
from the compressor 15. Optionally, the procedure may be repeated
for the second breast.
FIG. 2(a) shows a mammogram of the breast 17 in the first high
compression state. FIG. 2(b) shows a mammogram in the second low
compression state. It may be clearly seen that in the mammogram of
the first high compression state, more details are visible.
All the image data may be acquired by the detectors 5, 11,
respectively, as digital data and may be transferred to a computer
25 comprised in the control 19. The computer 25 is adapted for
acquiring the first, second and third image data and processing
these data.
For example, the computer 25 may derive an estimation of bulk
optical properties of the breast 17 from the acquired first image
data and use such estimated bulk optical properties in order to
improve reconstruction of the second image, i.e. a
three-dimensional optical tomography image, from the second image
data.
In a preferred embodiment, the computer 25 performs an elastic
registration of the two acquired mammograms, i.e. the first image
and the third image, in order to thereby derive information for a
deformation prior relating to the first and second compression
states of the breast 17.
Furthermore, the computer 25 may analyze a tissue composition of
soft body tissue within the breast 17 based on breast density and
dual energy spectral decomposition. Therein, information on tissue
composition of the breast in the region of interest may be derived
by taking into account the first image data and the third image
data acquired at different X-ray settings and analyzing differences
between these first and third image data. Details on possible
dual-energy volumetric breast density assessment may be derived
from European application No. 10194750.5.
Such estimated information on tissue composition may be
subsequently used in reconstructing the second image from the
second image data as such information on tissue composition may
serve for more precisely estimating bulk optical properties of the
breast in the region of interest. Accordingly, this information may
be used for more accurate volume of interest definition as
initialization for optical tomography reconstruction. Therein, the
volume of interest definition may not be linked to tissue
composition, but can be derived directly from the high spatial
resolution of the third image data alone. It is important to
mention that there is no deformation between second and third image
data.
Finally, the computer 25 may process the acquired image data for
displaying a registered superposition of a two-dimensional image
derived from the reconstructed second image and of a first image.
In other words, the local distribution of functional data as
derived from the second image data of the optical tomography image
acquisition and the structural data as derived from the first
mammography image may be registered and superpositioned. In order
to obtain a registered overlay of the structural data from the
mammogram acquired at normal compression and standard dose and the
optical tomography measurement acquired at reduced compression,
information comprised in the deformation prior as derived by
elastically registering the first and third image data may be used.
Finally, the overlaid first and second image may be visualized as a
fused image. Such visualization may be presented to a user, for
example on a display or may be printed out.
As such visualized fused image comprises both structural features
at high resolution from the mammogram and functional features from
the optical tomography image and, as furthermore, the optical
tomography image is of high quality as a result of using additional
information derived from the mammogram, such fused image may
provide valuable information to a physician in order to detect for
example cancerous tissue within the breast.
Finally, possible features, functions and advantages of embodiments
of the present invention may be summarized in a different wording
as follows.
Multimodal fusion of diffuse optical tomography (DOT) and
mammography promises to overcome deficiencies of both imaging
modalities by drawing on the strength of each thereby possibly
enabling synergy effects. Functional information with a spatial
resolution in the range of 10 millimeters is provided by optical
properties and high resolution structural image contrast is
generated using X-rays with spatial resolution of possibly less
than 0.1 millimeters. The DOT measurement may be integrated with a
mammography system.
However, DOT requires a lengthy measurement acquisition that may
add up to the acquisition time for a mammogram.
In order to improve patient comfort, it is desirable to perform DOT
at reduced breast compression.
This may introduce a correspondence problem between the result of
the DOT measurement and the mammogram, and may require an
estimation of a deformation field. Furthermore, DOT may be
sensitive to an estimation of bulk optical properties in order to
correctly interpret the measured response. Existing techniques with
optical cameras are only able to capture external deformation
without information about the internal structures of the breast. In
addition, it may be hard to determine optical properties accurately
from a single mammogram without precise knowledge about compression
height.
In other words, main disadvantages of combined mammography and DOT
acquisitions are long measurement times. Reduced breast compression
may improve the patient comfort but introduces a correspondence
problem: Mammograms have to be acquired at normal compression in
order to achieve sufficient visibility of structures for diagnostic
purpose; DOT measurements are performed at reduced compression
because of the long measurement time, but they lack structural
contrast and only provide functional responses at a coarse
resolution.
According to embodiments of the invention, such correspondence
problem may be overcome by using a deformation prior derived from
the registration of two mammograms.
Furthermore, the use of a single two-dimensional mammogram to
estimate bulk optical properties for DOT normalization may be
disadvantageous. Extracting tissue fractions from mammograms may be
highly susceptible to inaccurate compression height estimation and
therefore error-prone. According to embodiments of the invention,
such disadvantage may be overcome by complementing a first
mammogram with a dual energy pendant at reduced compression.
According to embodiments, the invention proposes a method to fuse a
digital mammogram with the result of a diffuse optical tomography
(DOT) at a different breast compression. DOT typically only
provides coarse resolution and requires structural information of a
complementary modality in order to allow spatial evaluation of the
data. Furthermore, DOT depends on estimated bulk optical
properties, i.e. different tissue types within the volume of
interest, in order to normalize the response. To improve patient
comfort during a lengthy DOT acquisition, it is desirable to
perform it at reduced breast compression. However, mammographic
image quality may strongly depend on a high breast compression.
Thus, it is proposed to acquire an additional low-dose radiograph
at reduced compression using different filter and/or energy
settings for X-ray acquisition.
According to embodiments of the invention, an additional low-dose
mammogram is exploited at the same reduced compression as used for
an optical tomography image acquisition. Using a deformable
registration scheme, it may be possible to derive a smooth
deformation field containing correspondences between pixels in the
mammogram acquired at normal compression and the follow-up
acquisition at reduced compression. These correspondences also
connect DOT and radiographic image data and thus allow an accurate
overlay of functional and structural image content.
To improve an estimation of bulk optical properties from the
mammogram(s) for normalization of the DOT results, it may be
possible to acquire the second mammogram with different photon
energy, target material and/or filter material. With such a dual
energy approach, relevant structures for a registration would still
be visible within the mammogram on the one hand and the
decomposition of the breast into different tissue types can be
performed more robustly using the two complementary energies,
compared to tissue type decomposition estimation from a single
mammogram. Moreover, high spatial resolution of the mammogram
acquired at the same compression level as the DOT acquisition may
allow for more accurate definition of a volume of interest for DOT
reconstruction.
It should be noted that the term "comprising" does not exclude
other elements or steps and that the indefinite article "a" or "an"
does not exclude the plural. Also elements described in association
with different embodiments may be combined. It should also be noted
that reference signs in the claims shall not be construed as
limiting the scope of the claims.
LIST OF REFERENCE SIGNS
1 imaging device 3 X-ray source 5 X-ray detector 7 exchangeable
filters 9 optical tomography light source 11 optical tomography
light detector 13 compression paddle 15 soft body tissue compressor
17 breast 19 control 21 housing 23 moving direction 25 computer
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